Active backplane for thin silicon solar cells

Abstract

Fabrication methods and structures relating to backplanes for back contact solar cells that provide for solar cell substrate reinforcement and electrical interconnects are described. The method comprises depositing an interdigitated pattern of base electrodes and emitter electrodes on a backside surface of a semiconductor substrate, attaching a prepeg backplane to the interdigitated pattern of base electrodes and emitter electrodes, forming holes in the prepeg backplane which provide access to the first layer of electrically conductive metal, and depositing a second layer of electrically conductive metal on the backside surface of the prepeg backplane forming an electrical interconnect with the first layer of electrically conductive metal through the holes in the prepeg backplane.

1 . A back contact crystalline semiconductor solar cell, comprising:
 a crystalline semiconductor substrate, said substrate comprising a light capturing frontside surface and a backside surface for forming emitter and base contacts;   a first electrically conductive metallization layer having an interdigitated pattern of emitter electrodes and base electrodes on said backside surface of said crystalline substrate, said first electrically conductive interconnect layer having a thickness less than approximately 10 microns;   a backplane attached to said backside surface of said crystalline substrate, said backplane laminated to said backside surface of said crystalline substrate and comprising a prepeg layer; and   a second electrically conductive metallization layer providing high-conductivity cell interconnects connected to said first electrically conductive interconnect layer via holes in said backplane, said second electrically conductive interconnect layer having an interdigitated pattern of emitter electrodes and base electrodes.   
     
     
         2 . The back contact solar cell of  claim 1 , wherein said second electrically conductive metallization layer is a copper layer. 
     
     
         3 . The back contact solar cell of  claim 2 , wherein said second electrically conductive copper layer is formed by a fully additive process. 
     
     
         4 . The back contact solar cell of  claim 2 , wherein said second electrically conductive copper layer is formed by a semi-additive process. 
     
     
         5 . The back contact solar cell of  claim 1 , wherein said holes in said backplane are laser-formed holes. 
     
     
         6 . The back contact solar cell of  claim 5 , wherein said holes in said backplane are laser-formed holes using a CO2 laser. 
     
     
         7 . The back contact solar cell of  claim 1 , wherein said crystalline semiconductor substrate has a thickness less than 100 microns. 
     
     
         8 . A method for forming a back contact solar cell, comprising:
 depositing a first layer of electrically conductive metal having an interdigitated pattern of base electrodes and emitter electrodes on a backside surface of a semiconductor substrate, said first layer of electrically conductive metal having a thickness approximately less than 10 microns;   attaching a prepeg backplane to said first layer of electrically conductive metal, said prepeg backplane providing electrical isolation between said first layer of electrically conductive metal and a second layer of electrically conductive metal;   forming holes in said prepeg backplane providing access to said first layer of electrically conductive metal; and   depositing said second layer of electrically conductive metal on the backside surface of said prepeg backplane forming an electrical interconnect with said first layer of electrically conductive metal through said holes in said prepeg backplane.   
     
     
         9 . The method of  claim 8 , wherein said step of forming holes in said prepage backplane is performed according to a laser annealing process. 
     
     
         10 . The method of  claim 8 , wherein said second layer of electrically conductive metal is copper. 
     
     
         11 . The method of  claim 10 , wherein said step of depositing said second layer of copper is performed according to a fully additive process. 
     
     
         12 . The method of  claim 10 , wherein said step of depositing said second layer of copper is performed according to a semi-additive process. 
     
     
         13 . The method of  claim 8 , wherein said step of attaching a prepeg backplane to said first layer of electrically conductive metal further comprises laminating said prepeg backplane to said first layer of electrically conductive metal. 
     
     
         14 . A method for forming a back contact solar cell, comprising:
 forming a porous silicon seed and release layer with at least two different porosities on the surface of a crystalline silicon template;   depositing an epitaxial silicon layer on said porous silicon seed and release layer, said epitaxial silicon layer having a thickness less than 100 microns and an in-situ-doped base region, and said epitaxial silicon layer comprising doped emitter regions and a backside surface for forming emitter and base contacts with said in-situ-doped base regions and said doped emitter region;   depositing a first layer of electrically conductive metal having an interdigitated pattern of base electrodes and emitter electrodes on said backside surface of said epitaxial silicon layer, said first layer of electrically conductive metal having a thickness less than 2 microns;   depositing a first layer of electrically conductive metal having an interdigitated pattern of base electrodes and emitter electrodes on a backside surface of a semiconductor substrate, said first layer of electrically conductive metal having a thickness approximately less than 10 microns;   laminating a prepeg backplane to said first layer of electrically conductive metal, said prepeg backplane providing electrical isolation between said first layer of electrically conductive metal and a second layer of electrically conductive metal;   forming holes in said prepeg backplane according to a laser process, said holes providing access to said first layer of electrically conductive metal; and   depositing said second copper layer on the backside surface of said prepeg backplane according to a semi-additive process forming an electrical interconnect with said first layer of electrically conductive metal through said holes in said prepeg backplane.